This application claims the benefit of Korean Patent Application No. 2003-100621, filed on Dec. 30, 2003, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein in its entirety by reference.
1. Field of the Invention
The present invention relates to microfluidics, and more particularly, to an ultra small fluorescence detector capable of detecting reaction of a microfluid in a microfluid device.
2. Description of the Related Art
A microfluid chip is a chip capable of containing and manipulating a trace of fluid by covering a microchannel structure produced using a microprocessing technology such as lithography, hot embossing, and molding, with a cover. The microfluid chip can reduce the amount of reagent consumed and shorten the analysis time.
In particular, when DNA denaturation, annealing, and extension require different temperatures as in a polymerase chain reaction (PCR), the reactions are undergone by repeating a temperature cycle. In this case, a small reaction volume and broad area can rapidly transfer temperature in a micro chamber, thereby reducing the time required for the temperature cycle.
There are various methods of detecting a PCR in real time; however, fluorescence detection is currently preferred. A variety of methods such as a method using a dye and a TaqMan(R) method have been developed for fluorescence detection. In the method using a dye, a dye such as SYBR Green I, which improves fluorescence by binding to double-stranded DNA produced in a PCR, is used. In the TaqMan(R) method, a DNA sequence capable of binding between two primers other than a primer used in a PCR is used as a probe, and a fluorophore and a quencher are bound to both ends of the probe. When cutting the probe using exonuclease activity of Taq polymerase used in DNA synthesis, the DNA bound between the fluorophore and the quencher is cut, and thus, the bond between the fluorophore and the quencher is broken. At this time, the emitted fluorescence is analyzed.
Meanwhile, U.S. Pat. No. 5,928,907, entitled “System for Real Time Detection of Nucleic Acid Amplification Products”, issued on Jul. 27, 1999, and which is assigned to Applied Biosystems, discloses a method of detecting fluorescence in a tube using optical fibers as one of the methods of detecting fluorescence. In this case, one detector can detect a number of tubes. However, an expensive light source having good coherency, such as a laser, must be used to collect an excitation beam for exciting fluorescence on optical fibers. Furthermore, a precise optical device is required, thereby increasing the price of the apparatus.
In a method disclosed in U.S. Pat. No. 6,369,893, entitled “Multi-Channel Optical Detection System”, issued on Apr. 9, 2002, and which is assigned to Cepheid, an excitation block and a detection block are divided. Fluorescence excitation is performed by an LED in the excitation block, and a fluorescent signal is detected in the detection block arranged at an angle of 90 degrees with respect to the excitation block. Thus, this apparatus is advantageous to modularization.
However, since excitation and detection are achieved at a side wall of a diamond-shaped tube in order to perform excitation and detection at an angle of 90 degrees, the tube must have sufficient wall thickness. Thus, the volume of a sample tube must be 25 μl or more.